1. Technical Field
This technology pertains generally to chip-to-chip communication, and more particularly to phase-synchronization in short-range chip-to-chip communication utilizing differential current mode multiple-frequency modulation-demodulation.
2. Background Discussion
Serial I/O between integrated circuit “chips,” or other devices, is typically based on multiplexing and demultiplexing digital communications. To increase communications bandwidth using these conventional schemes, one first turns to increasing the clock rate. However, each process technology has its own limitations on clock rates, whereby one must often increase the number of I/O connections to increase the bandwidth, and as a result manufacturing costs increase. These costs are even further increased in 3D integrated circuit integration, such as those based on through-substrate-via (TSV) for vertical interconnections. The number of TSVs for the I/O is non-scalable due to fundamental physical or mechanical constraints. Higher than a certain number of TSVs per unit area (or population density) leads to thinned Si substrate (about 100 μm/tier) which can result in collapse. Therefore, this thinning can seriously limit inter-tier communication bandwidth in 3D integrated circuits.
Thus, chip-to-chip communication circuits with higher communication bandwidths have been sought which do not require concurrent increases in the clock rate or additional I/O connections.
However, problems arise with these circuits when used in radio frequency (RF) communications in regard to phase synchronization for optimizing signal strength recovery. Existing methods to perform this phase synchronization between modulation and demodulation is performed utilizing digital signal processing and requiring complex circuitry which is subject to high power consumption levels. Although this traditional method offers flexibility of phase tuning capability by using software DSP, its long latency and large hardware overhead make the approach less preferable for short latency, low power, and simple circuit topologies, such as required for mobile and micro-server applications.
Accordingly, our technology described below provides enhanced multiple-band modulation and demodulation synchronization for RF communications, such as for chip-to-chip TSV-link communications.